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Neo Geo MVS, incompatible with SuzoHapp CGA LCD?

Bit further along now, got the web UI to load on an old Samsung I keep around for this sort of thing and confirmed that I'm getting a video signal through the modified GBS. Now I just need to build a wiring harness. Also need to secure the PCBs a bit better. Using velcro right now and it's a bit wobbly.
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More progress, while still working on a proper wiring harness for the 10 pin CGA out of my cabinet I hooked things up to a super gun and have confirmed that my 256 (in 246+ mode) works great out of the modified GBS. This is one of the systems that I couldn't get sync from using the scaler built into the Happ LCD. Note that I am using my bench 17" Viewsonic LCD here, but the principal should be the same. Picture is clean, with no noticeable artifacts or latency. I played around a bit with the filter options, smoothing, scan lines, etc but I think the stock output looks best (to me at least). Web controls for aspect ratio, position, scale, etc work great.

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OK... so built the wiring harness. Tested it out, and it's "OK". Not great. The Happ LCD keeps trying to auto-adjust and I can't figure out how to get it to stop. Also not sure of what it's native resolution is, which makes adjusting the output from the GBS tricky. The biggest issue, is that it's not working with my MVS-2F. Seems fine on my 1B, but the 2F is dropping at least every other frame through the GBS (but it worked, showing the overscan wavy image, when using the native firmware). This may be indicative of a problem with the 2F... I may have a failing capacitor or two, causing the output sync frequency to fluctuate(?). Will try hooking up my bench LCD to the cabinet. If that works, I may just give up on the Happ and use the Viewsonic (will be tricky to mount it as it's a closed frame with a VESA mount).

Edit: It's 1280x1024... which isn't a great resolution to scale 15khz too. And it doesn't always like the 1280x1024 signal out of the modified GBS. No clue about the 2F yet. But everything else mostly works.

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Just occurred to me to not only remove the jumper to to reset the GBS to factory firmware, but also pull power from the Arduino. Now the MVS-2F works with the LCD. Kinda... it displays, no dropped frames, but has a hard time locking onto the sync signal. But I think that's as well as it worked before. I may need to think about recapping the 2F (not sure that's the issue, but it feels right).
 
Update: With the help of some redditers I found the issue. Looks like a commit to the GBS Control GIT code broke compatibility with Neo Geo.

Here's the issue thread on GIT which goes into more detail as to what's happening.

Going back to the old version of GBS-Control from prior to the commit, and it does work. But the old UI is really a pain to use... output quality isn't bad though (needs a bit of adjusting to center it).
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And now it's not working with CPS1... but I think I'm spending too much time getting the LCD working as a procrastination method for recapping and tuning the CRT.

Edit: today it IS working with CPS1... probably a PEBCAK error.
 
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End results, simple plywood cutout for the LCD, held in place with some clamps. Modified GBS velcroed on the back with a y-cable so everything is powered of a single 12v source. All in all, it's not too bad. Can definitely live with it for now and find another use later (thinking a coffee table cab).
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